twalthr commented on a change in pull request #7177: [FLINK-7599] [table]
Support for aggregates in MATCH_RECOGNIZE
URL: https://github.com/apache/flink/pull/7177#discussion_r237488275
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File path: docs/dev/table/streaming/match_recognize.md
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@@ -211,6 +211,66 @@ If a condition is not defined for a pattern variable, a
default condition will b
For a more detailed explanation about expressions that can be used in those
clauses, please have a look at the [event stream
navigation](#pattern-navigation) section.
+### Scalar & Aggregate functions
+
+One can use scalar and aggregate functions in those clauses, both
[built-in]({{ site.baseurl }}/dev/table/sql.html#built-in-functions) as well as
provide [user defined]({{ site.baseurl }}/dev/table/udfs.html) functions.
+
+Aggregate functions are applied to subset of rows mapped to a match. To
understand how those subsets are evaluated have a look at the [event stream
navigation](#pattern-navigation) section.
+
+With a task to find the longest period of time for which the average price of
a ticker did not go below certain threshold, one can see how expressible
`MATCH_RECOGNIZE` can become with aggregations.
Review comment:
Introduce a subsection `Example` as done in other sections?
Rephrase: `The task of the following example is to find... threshold. It
shows how...`
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